In an exemplary conventional motorcycle, a seat on which a rider is seated is placed behind a fuel tank. To allow the rider to be seated on the seat in a straddle position, the right and left sides of the seat are open. Further, a motorcycle seat is disclosed, which includes side support members for allowing the rider to be well fitted to the right and left sides of the seat to improve comfort (e.g., see Patent Literature 1). In this motorcycle, the seat is extended in a width direction thereof to form the side support members.